1. Technical Field
The present invention relates to antennae in general, and, in particular, to a conductor having two frequency-selective surfaces.
2. Description of Related Art
Antenna systems capable of providing independent operations in different directions have been widely utilized in microwave relay systems for long haul point-to-point applications (largely replaced by buried fiber optic cable in conventional systems), and, more recently, sectorized antenna systems for mobile telephony, or cellular telephones. Antenna systems capable of providing independent operations in different directions are typically large and mechanically complex, and are constructed of parabolic reflectors (as in microwave relay stations) or multiple metallic structures (as in cell antennas). Similarly, planar antennas have been utilized on the skin of aircraft and in massive phased array structures for electronic beam steering. Planar arrays have not been used in applications where independent operations are required in different directions.
Any arrangement of surfaces that provide high impedance for surface currents is referred to as a high impedance surface (HIS). If an electric field antenna is placed in close proximity to a HIS that includes a frequency-selective surface (FSS) in close proximity with a perfect electrical conductor (PEC), the energy reflected from the HIS will return in phase with the energy radiating away from the HIS, thereby amplifying the antenna signals. Such arrangement allows efficient, low-profile planar antennas and arrays to be constructed using pattern and etch techniques like those developed for printed circuit boards.